Couplings for high pressure lines, particularly those intended to use subsea, are customarily self operating, normally comprising a female coupler or receiver and a male coupler or probe insertable in the receiver. The couplers include mutually engageable means, normally spring loaded poppet valves, which engage when the couplers are mated so that high pressure fluid can flow from one coupler to the other couplers. It is necessary to provide at least one seal between the couplers and normally at least two seals therebetween in order to prevent egress of hydraulic working fluid from the coupling. Such seals must be extremely durable and reliable because the couplings are usually required to remain subsea for very long periods of time.
A variety of different forms of seal have been proposed for such couplings. They include crush seals between axially confronting parts of the couplers and, more recently, pressure-responsive resilient metal seals, usually with a C-section. An examples of the latter form of seal is given by U.S. Pat. No. 4,694,889, which describes a coupling in which a C-seal is retained in an annular shoulder in the bore of the female coupler by means of an insert within the body of the coupler. The C-section of the seal faces towards the region of the poppets and its inner periphery engages the outer periphery of the male coupler. A seal of this kind is laterally expanded, both inwardly and outwardly, by internal pressure from the couplers and forms a respectively dynamic radial seal with both the receiver and the probe. A similar seal is provided in the couplings described in U.S. Pat. Nos. 4,768,538 (Mintz et al.) and 4,834,139 (Fitzgibbons).
As remarked above, it is preferable to provide at least one other independent seal between the probe and the receiver. The aforementioned patents disclose the provision of an additional elastomeric O-ring seal retained in an annular internal groove in the female coupler and engaged by the male coupler.